Three U.S. drone strikes killed a total of 12 suspected al-Qaeda terrorists Thursday — the sixth, seventh and eighth such attacks in less than two weeks as the Arab nation is on high alert against terrorism.

The increase in drone strikes signals that the Obama administration is stepping up its efforts to target Yemen’s al-Qaeda offshoot — al-Qaeda in the Arabian Peninsula — amid fears of attacks after the interception of a message between its leader and the global leader of the terror network.

Since July 27, drone attacks have killed 34 suspected terrorists, according to Yemeni security officials.

The Yemeni military official said the first drone attack Thursday killed six alleged terrorists in central Marib province, while the second killed three more in the al-Ayoon area of Hadramawt province in the south. A third strike killed three suspected terrorists travelling in the al-Qutn area of Hadramawt

All the airstrikes targeted cars, added the official, who spoke on condition of anonymity because he was not authorized to talk to the media.

The high alert in Yemen came after authorities revealed an al-Qaeda plot to target foreign embassies and international shipping lanes in the Red Sea.

The U.S. and Britain evacuated diplomatic staff this week after learning of a threatened attack that prompted Washington to close temporarily 19 diplomatic posts in the Middle East and Africa.

While the United States acknowledges its drone program in Yemen, it does not confirm individual strikes or release information on how many have been carried out.

The program is run by the Pentagon’s Joint Special Operations Command and the CIA, with the military flying its drones out of Djibouti, and the CIA out of a base in Saudi Arabia.

Yemeni authorities said Wednesday they uncovered an al-Qaeda plot to target foreign embassies in Sanaa and international shipping in the Red Sea.

A U.S. intelligence official and a Mideast diplomat have said the embassy closures were triggered by the interception of a secret message between al-Qaeda chief Ayman al-Zawahri and Nasser al-Wahishi, the leader of the Yemen-based al-Qaeda in the Arabian Peninsula, about plans for a major attack.

The discovery of the al-Qaeda plot prompted the Defence Ministry to step up security around the strategic Bab el-Mandeb waterway, which connects the Red Sea with the Gulf of Aden. Officials banned speedboats and fishing vessels from the area, and military forces have been ordered to shoot to kill anybody who arouses suspicion or refuses to identify themselves.

Details of the plot were reminiscent of the suicide attack on the USS Cole in 2000 in Aden harbour that killed 17 American sailors.

Yemeni troops have stepped up security across Sanaa, with multiple checkpoints set up and tanks and other military vehicles guarding vital institutions. The army has surrounded foreign installations, government offices and the airport with tanks and troops in the capital, as well as the strategic Bab al-Mandeb straits at the entrance to the Red Sea in the southern Arabian Peninsula.

The terror network’s Yemeni offshoot has been bolstering its operations in Yemen more than a decade after key Saudi operatives fled here following a major crackdown in their homeland.

The al-Qaeda group overran entire towns and villages in Yemen in 2011, taking advantage of a security lapse during nationwide protests that eventually ousted longtime ruler Ali Abdullah Saleh. Backed by the U.S. military, Yemen’s army was able to regain control of the southern region, but al-Qaeda terrorists continue to launch deadly attacks on security forces.

The drone strikes, which became a near-daily morning routine starting July 27, have been concentrated so far in remote mountainous areas and valleys where al-Qaeda’s top five leaders are believed to have sought refuge.

A senior security official said the al-Qaeda leaders never meet together out of fear of a drone attack killing all of them at once. These include Nasser al-Wahishi, a onetime aide to Osama bin Laden; Qassem al-Raimi, believed to be the military commander; and Ibrahim al-Asiri.